1. Field of the Invention
The present invention relates to a method and system for fusing a spinal region. More particularly, the present invention relates to minimally invasive intravertebral disc distraction, rotation, or translation, removal of disc and/or vertebral bone material, and subsequent fusion of a disc.
2. Description of Related Art
There are five movable vertebrae in the lower back. This area is called the lumbar spine and is the flexible part of the back. Above the lumbar spine is the thoracic spine and below it is the sacrum and coccyx. Between each vertebra is a cushion referred to as an intervertebral disc. Each disc has a tough exterior rim of fibrous cartilage (similar to that of a radial tire), referred to as the annulus fibrosis. Within each disc is a resilient and “jelly-like” interior filling, referred to as the nucleus pulposus. The top and bottom of the disc are covered by relatively bony endplates.
FIG. 1 is a partial cross-section view of a portion of the spine. As shown in this figure, an intervertebral disc D is positioned between adjacent vetebral bodies V1 and V2 and includes an annulus fibrosis A, a nucleus pulposus N, and end plates EP. Positioned on the vertebral bodies V1 and V2 are a superior articular process SAP, a pedicle P, an inferior articular process IAP, a spinal process SP, and a facet joint FJ.
Each disc and the vertebra above and below it compromise a motion segment. Movement such as bending forward (flexion) bending backwards (extension) and twisting and turning (rotation) occur at these motion segments.
Approximately 80% of the American population experiences various forms of lower back pain at some point during their lifetimes. Back pain is sometimes associated with intervertebral disc trauma, degeneration of the disc or joints in the spine, disc herniation, spinal instability, bone spurs, or inflamed ligaments. Back pain can also be caused by an injury, disease, malalignment, tumor, hereditary weakness, and previous back surgery. In addition, back and/or leg pain may be caused by pressure on the spinal cord or on a spinal nerve. Techniques for treatment vary from simple interventions such as rest and physical therapy to more complicated surgical procedures such as spinal fusions. (As used herein the term “fusion” refers in general to increasing the stability of a region of the spine, and does not necessarily require the physical joining of portions of the spine.) Some surgical techniques have improved to the point where invasiveness and trauma to non-spinal tissues can be kept to a minimum.
Intervertebral discs commonly wear and tear, weakening their outer fibrous structure. Increasing pressure in the spine may bulge and even rupture the disc, causing back or leg pain. In normal aging, discs lose water and decrease their ability to function as “shock absorbers.” Narrowing discs increase stress to the facet joints.
Instability or abnormal motion may occur in the advanced stages of arthritis or from trauma. Spondylolithesis is a forward slipping of one vertebra over another and may result of severe instability. Spinal stenosis, a narrowing of the spinal canal, may be a result of arthritis, putting pressure on the nerves or the spinal cord. Osteoarthritis may result in narrowing of the disc spaces and development of bone spurs on the vertebral bodies.
Herniated discs are another form of injury to the intravertebral disc and are often referred to as “slipped discs.” This term is derived from the action of the nucleus tissue when it is forced from the center of the disc. The disc itself does not slip. However, the nucleus tissues located in the center of the disc can be placed under so much pressure that it can cause the annulus to be herniated or rupture against one or more of the spinal nerves which can cause pain, numbness, or weakness in the lower back, leg or foot. Other names used for herniated discs are “prolapsed,” “bulging,” or “ruptured.” Depending on the results of a physical examination and the severity of the condition, physicians commonly offer one of two forms of treatment. The first common treatment is “conservative therapy,” comprising bed rest, pain medication, and physiotherapy.
If conservative therapy does not bring enough pain relief, surgical procedures are typically considered. The most common reason for recommending lower back surgery is to relieve either back or leg pain. To decrease leg pain, pressure is removed from the affected spinal nerve. Removal of a tumor, treatment of a fractured spine, and repair of malalignments are other reasons surgery is undertaken. In order to accomplish these objectives, the spine surgeon may remove the disc (discectomy) or a part of the lamina (laminotomy) or remove the whole lamina (laminectomy). The procedure is also referred to as a decompression because the pressure on the nerve or the spinal cord or cauda equina is removed.
Sometimes motion between the vertebral bodies must also be stopped in an effort to relieve pain. In such cases, the surgeon may elect to perform a spinal fusion procedure. This procedure entails implanting pieces of bone graft, usually obtained from the patient's own iliac crest bone (hip). The bone graft is intended to encourage bone growth between the vertebral bodies and the posterior aspect of the spine. If the bone develops and grows between the vertebrae, then the spine segment is said to have “fused,” and the motion between the vertebral bodies is therefore eliminated.
Fusion is best accomplished when the vertebrae are kept as motionless as possible during the healing process which is usually four to six months. Physicians may recommend achieving stability through additional internal fixation devices attached to the vertebral bodies during the surgical procedure. This may be performed with a combination of screws inserted meticulously into the vertebral body and attached to one another with a series of rods, plates, wires, or hooks.
Until a few years ago, the only surgical treatment for herniated lumbar discs was the open removal of a part of the herniated disc, an often effective but major operation that requires general anesthesia, the dissection of muscle, removal of bone, and at times, bone fusion. These procedures increase the risk to the patient of post-operative complications.
In recent years, techniques employing the use of endoscopy have been incorporated into lumbar spine surgery making minimally invasive spine surgery possible while overcoming disadvantages of traditional techniques. Endoscopic discectomy can provide an effective way to decompress and repair damaged discs without open surgery. An endoscope provides clear visualization and magnification of deep structures. First used in knee surgery, endoscopy (arthroscopy), with its advanced miniaturization and video imaging technology, has made it possible for a less invasive and less traumatic discectomy procedure for some disc patients.
Endoscopic discectomy is an outpatient surgical procedure to remove herniated disc material. Using local anesthesia with the help of x-ray flouroscopy and magnified video for guidance, a small specially-designed endoscopic probe is inserted through the skin of the back, between the vertebrae, and into the herniated disc space. Tiny surgical attachments are then sent down the hollow center of the probe to remove a portion of the offending disc. The microsurgical attachments can also sometimes be used to push the bulging disc back into place and for the removal of disc fragments and small bony spurs.
Endoscopic discectomy is different from open lumbar disc surgery because there is no traumatic back muscle dissection, bone removal, or large skin incision. The risk of complications from scarring, blood loss, infection, and anesthesia that may occur with conventional surgery are drastically reduced or eliminated with this procedure. Endoscopic discectomy was invented to be an effective treatment for herniated discs while avoiding these risks.
A wide variety of spinal implants are available to the clinician for the surgical treatment of spinal disorders. Most of the implants are designed to promote long term fusion. For certain conditions, anterior fusion of the lumbar spine is a standard operation. Despite improvements in fusion techniques and reductions in the pseudoarthritis rate, improved procedures and devices are needed. Surgeons specializing in operations on the vertebral column necessarily incorporate laparoscopic surgery. Other concepts such as the biological enhancement of spinal fusion and alternatives to fusion such as artificial discs and interbody cage devices are the object of intense, multidisciplinary study. Despite these improvements, currently there are neither devices designed to distract the intervertebral disc percutaneously nor minimally invasive procedures to achieve spinal fusions.
In light of the foregoing, there is a need in the art for improving procedures and devices associated with performing spinal surgery.